PROJECT SUMMARY/ABSTRACT Habits are inflexible and automated behaviors that can be advantageous by freeing cognitive resources. However, brain circuits subserving habits are overactive in disease states including drug addiction, Obsessive Compulsive Disorder, and Tourette's syndrome. A key brain region in behavioral selection is the striatum, which receives inputs from midbrain dopamine neurons. Striatum is often divided into a medial and lateral portion, and disruption of lateral striatum or lateral dopamine inputs interferes with habit formation, while disruption of medial striatum promotes habit. Additionally, lateral striatum dopamine release only emerges late in learning, when habitual behaviors arise, suggesting that lateral striatum dopamine release is a key mechanism in habit formation. However, no studies have investigated a causative link between medial or lateral dopamine release and habit formation. In addition to this medial/lateral divide, striatum has neuroanatomically distinct `patches', which make up ~15% of striatum and which provide the only direct, inhibitory output from striatum to dopamine neurons. Previous work suggests patches are active during repetitive behaviors and that modifying patch activity alters decision making. Thus, patches may play a role in the transition from flexible to habitual behaviors, though no studies have investigated this possibility. Therefore, this proposal aims to determine 1. if activating lateral striatum dopamine inputs is sufficient to establish habitual responding 2. if striatal patches are necessary for habit formation and 3. the activity of striatal patch and dopamine neurons during habit formation. This work will yield crucial insights into striatal subcircuits driving habitual behaviors and may yield new therapeutic targets for remediating diseases characterized by maladaptive habits. Further, these projects will provide an opportunity to train the next generation of Oberlin College undergraduate researchers to use cutting-edge neuroscience techniques, to analyze and present behavioral and physiological data to their peers, and to navigate experimental design and the scientific process. By providing training opportunities in optogenetics, viral approaches, fiber photometry, and behavioral assays, this proposal will facilitate the education of Oberlin College researchers and enhance to the research environment at Oberlin College.